Fuel problem on my 7.4 l

[SmallsTX]

Ok so I have a 1980 c35 with a 454. I'm not getting but a mile per gallon.
My fuel tank is a 5 gallon gas jug at the moment. My fuel returns arnt getting any gas threw them and I have my number 3 spark plug gas fouled.

 

[1987 GMC Jimmy]

Holy crap! Do you have a return pump first of all? Someone may have stuck the one with just the inlet and the outlet and capped the return. Or worse, just left it hanging there. I’d check your timing and do an ignition tune up (also make sure you have a “hot” spark) but this sounds like way too much fuel being metered by the carb. What carb do you have on it?

 

[SmallsTX]

Holy crap! Do you have a return pump first of all? Someone may have stuck the one with just the inlet and the outlet and capped the return. Or worse, just left it hanging there. I’d check your timing and do an ignition tune up (also make sure you have a “hot” spark) but this sounds like way too much fuel being metered by the carb. What carb do you have on it?

Well no not really on the return pump. My fuel pump is on the block. But my fuel line is ran directly from a 5 gallon gas tank straight to the carb. And I'm running a 700cfm quadrajet and a rebuild on the carb is probably needed.

 

[1987 GMC Jimmy]

Right, but the return pumps will have a smaller, third nipple. You’d need one of those to get the fuel return working. Yeah, I would rebuild the carb or have it done. It’d be a good idea to check the jetting, but it’d probably just needs a rebuild and a proper tuning.

 

[SmallsTX]

Right, but the return pumps will have a smaller, third nipple. You’d need one of those to get the fuel return working. Yeah, I would rebuild the carb or have it done. It’d be a good idea to check the jetting, but it’d probably just needs a rebuild and a proper tuning.

The fuel pump does have the 3rd nipple my old line might be crimped some where so I'll just undo it and see if any fuel comes back.

 

[bucket]

There's too much focus on that return hose. It really doesn't do much.

One mile per gallon? You are driving around using a 5 gallon jug? That's around 4.5 miles of range.

 

[SmallsTX]

There's too much focus on that return hose. It really doesn't do much.

One mile per gallon? You are driving around using a 5 gallon jug? That's around 4.5 miles of range.

Yea I know it's just till I get a fuel cell. I don't take it off the property rite now. Later on to day I'm going to check the compression. Also my fuel line keeps alot of pressure in it between the carb and the pump

 

[bucket]

Ok, so you don't actually know what the mpg is. That makes more sense, lol.

The fuel pump is only capable of putting out around 5 psi or so. The needle and seat in the carb are designed to handle that. If there was excessive fuel pressure, it would be causing the carb bowl to overfill and fuel would be pouring out of the bowl vents.

Like I said before, that return line really doesn't do much at all. It's not at all like the return line on a fuel injection setup.

 

[SmallsTX]

Well I know I should be getting more than 5 miles out of that jug, defiantly since I'm just putting around the property.

 

[bucket]

Well I know I should be getting more than 5 miles out of that jug, defiantly since I'm just putting around the property.

And that's exactly why. Idling and putting around is how worst mileage is acheived.

 

[bucket]

Useable mileage figures are impossible to obtain without driving long distances.

 

[SmallsTX]

#5 plug is fouled also